Birth Weights Decrease in the U.S.

Over the past half century, birth weights have increased at a steady pace. But a recent study conducted at the Harvard Care Institute’s Department of Population has revealed quite a different and surprising trend. From 1990 to 2005, birth weights have actually decreased in the United States.

This study analyzed more than three million babies born in the United States between these 15 years. Factors were taken in to consideration during the study such as the birth mother’s age, hypertension risk, health, tobacco and alcohol use, marital status, race, ethnicity and weight.

Researchers also took in to consideration the amount of time it took before the expectant mothers began receiving prenatal care. And finally, the use of cesarean delivery and obstetric procedures was calculated into the study’s formula.

The most notable decrease in birth weight began in 1995. Between the entire span of the study, babies were born on an average of 1.83 ounces (52 grams) less than those in previous years.

Interestingly, the average gestation length of babies born full term decreased by two days. This may be due to an increase in cesarean procedures in the United States as well as an increase in induced births.

Women in poor living conditions, minorities and those with increased health risks did not rank the highest in babies born with lower weights. Rather, non-smoking mothers who were white, married, well educated and delivered their babies vaginally averaged babies weighing 2.8 ounces less than other women in the study.

What can cause a low birth weight baby? The March of Dimes reports that women who previously delivered premature babies are at a greater risk for having future low weight infants. Women pregnant with multiples often deliver lower weight babies as well.

Women who smoke, drink alcohol or take drugs while pregnant are in this risk category. Social-economic factors, health problems and infections in both mother and baby can cause low birth weight babies too.

This Harvard study is guaranteed to raise future questions regarding pregnant women and the growing number of babies born at lower birth weights.